Multiple display computer systems have been proposed for many applications.
One type of such applications involves enlarging the graphical desktop of a graphical user interface (GUI) operating system by spreading the graphical desktop over multiple displays. Such an enlarged desktop is particularly advantageous for certain graphically intensive environments such as CAD, video editing and financial programs. For example, when editing video chips, one display can be operated in a high resolution mode as the system display to provide user interface support, while the other display displays the work in progress or edited chip. In the financial environment, multiple displays can be used for displaying large spreadsheets or multiple applications.
The architecture employed to implement such multi-display systems has generally mirrored the architecture employed in conventional single display systems only in multiple form. That is, each display in such systems has typically included its own graphics chip with an associated memory device or frame buffer. Moreover, in this architecture, each graphics chip receives operating system driver calls only for its own display. In this regard, a software driver interface operates between the operating system and the graphics chips to, among other things, separate driver calls from the operating system (which normally has been designed to expect only a single display) into separate calls for the multiple chips. Such systems make effective use of multiple monitors but require significant hardware support which increases costs.
Another type of multiple monitor system has been developed for specific laptop applications such as presentation support. This type of system supports one digital display output and one analog display output. In the presentation environment, the digital output is used to drive the LCD display of the speaker's laptop. The analog output can be used to drive a CRT monitor viewed by the audience. The architecture for this type of system employs a single graphics chip with a single frame buffer to provide the digital and analog outputs. Such systems make efficient use of hardware but are limited to mixed digital/analog display environments.